1. Field of the Invention
The present invention generally relates to a method and an apparatus for drying semiconductor wafers. In particular, it relates to a method and an apparatus for drying semiconductor wafers using an IPA dryer in which the semiconductor wafers are dipped in a liquid IPA prior to drying in an IPA dryer.
2. Description of the Related Art
Recently, IPA dryers have been used for the drying of semiconductor wafer, because compared to a spin dryer, the semiconductor wafers incur less mechanical damage and a cleaner semiconductor wafer surface is obtainable.
A typical IPA dryer is shown in FIG. 1. An IPA dryer 100 is isolated with shutters 201 and 202 to isolate the semiconductor wafers to be dried from oxygen and to reduce the water content contained in the semiconductor wafers. Semiconductor wafers 10, for example which have been washed after a wet etching step, are delivered by a mechanical arm 20 to the IPA dryer 100 for drying. IPA (Isopropyl Alcohol) L.sub.1 contained therein is heated by a hot plate 14 to its boiling point to generate IPA vapor L.sub.2 in the dryer 100. The semiconductor wafers 10 are supported by a holder 110, and are surrounded by cooling or condensation coils 130 disposed on the inner peripheral surface of the dryer 100. The IPA vapor L.sub.2 condenses on the semiconductor wafers 10 5 when rising to the level of the cooling coil 130, and then removes contaminants from the semiconductor wafer 10. The IPA condensate which contains the contaminants then drips from the semiconductor wafer 10 to a collecting tray 120 mounted at the bottom of the dryer 100 and is drained out from an outlet 121. However, if any water from the previous washing step remains on the semiconductor wafer 10 before being delivered in the dryer 100 for drying with the IPA vapor L.sub.2, the dried semiconductor 10 has water markers formed on the surface thereof.